1. Field of the Invention
The present invention pertains to air purifying hood masks, or more particularly to air purifying, particulate respirator hoods for use in contaminated military environments.
2. Description of the Related Art
Air purifying, respiratory protective devices currently used by the military for protection against chemical and biological contaminants impose a substantial physiological burden on the wearer. These respirators (masks) are difficult to wear for prolonged periods because they are relatively bulky and heavy, have high breathing resistance, impair vision and communications, cause thermal stress and discomfort, and degrade job performance. Most of the encumbrance associated with wearing military masks is attributed to the filter element that is specifically designed to protect against a broad spectrum of chemical warfare agents. Military mask filters typically contain two types of media; an activated carbon media for gas/vapor adsorption and a high efficiency particulate air (HEPA) media to protect against aerosol threats such as agents of biological origin (e.g., bacteria, viruses, and toxins). These filters are inherently bulky and have high breathing resistance (45-55 mm H.sub.2 O). A number of military and civilian uses exist where protection against biological agents or other particulate hazards is the sole concern. Such scenarios only require an air-purifying particulate respirator equipped with a HEPA filter that by definition is capable of removing at least 99.97% of all airborne particulate hazards in the form of aerosols. There are a number of commercially available half-mask, full-facepiece, and hooded escape respirators that could be used for biological protection. However, all of these have significant shortcomings that are overcome by the present invention. Although lighter in weight and less burdensome, the main shortcoming of half-mask respirators is that they do not seal as well as full-facepiece masks and escape hood respirators with a tight-fitting neck seal. Another disadvantage of half-masks is that they offer no protection for biological agents that harm and/or enter via the eyes. Full face respirators provide eye protection, however, their main disadvantages are that they are bulky, heavy, and uncomfortable and thus difficult to wear for prolonged periods of time. Commercially available escape hood respirators, also known as self-rescue respirators or smoke hoods, also protect the eyes, however, these devices are designed for only short-term protection, for example during self-rescue from a fire. Although they may provide adequate protection against certain gas, vapor, and particulate contaminants such as fire combustion products, most air-purifying escape hoods are not equipped with a HEPA-quality filter and thus afford insufficient protection against submicron aerosol hazards such as biological warfare agents. The major disadvantage of currently available escape hood respirators is that they are constructed of air-impermeable materials that impose a significant heat burden to the wearer. Fogging of the facepiece lens is also a serious problem with escape hood respirators due to perspiration and heat buildup under the hood. Another potential problem is the buildup of harmful levels of carbon dioxide within the hood. This is especially true of escape hoods that are not equipped with a nosecup and are loose fitting. As a result, escape hoods can only be worn for a short period of time. The invention described herein overcomes the shortcomings described above with current state-of-the-art air-purifying HEPA hood respirators that could be used for protection against biological hazards. Unlike commercial escape hood respirators, the present invention has several unique design features that enable it to be worn for extended periods of time. A high-tech, elastic, "breathable" fabric provides a lightweight, form-fitting, comfortable hood that permits moisture to escape yet is impermeable to aerosols. The hood is also equipped with low-resistance, electrostatic HEPA filters and incorporates an air management system to prevent fogging. These and other unique features function together to greatly increase user comfort and wear time. The hood benefits a military or civilian user whose duties demand a less cumbersome, more comfortable, highly protective respirator to prevent exposure to biological warfare agents. For example, the hood could be used to protect law enforcement, security, and health care personnel who are responsible for the evacuation, transportation, and treatment of biological casualties resulting from a terrorist attack. Likewise, Special Forces and other military users could use the hood as a precautionary measure for reconnaissance missions or for sleeping when a less encumbering lower level protective posture is required. In addition to military and counter-terrorism operations, the present invention has potential commercial applications. For example, the hood could be used in the health care industry for protection against airborne infectious diseases such as tuberculosis. The HEPA-quality particulate filters allow the hood to be worn by workers for protection against hazardous industrial aerosols such as asbestos and lead dust.